Rotor structure for a motor

ABSTRACT

A rotor structure for a motor includes a shaft, a single magnet and two fixing seats. The single magnet has two opposite end faces. An axial hole has a maximum extent equal to a maximum extent between the two opposite end faces. At least one of the two opposite end faces has a first engaging member. The magnet and each opposite end face have a maximum radial extent. Each fixing seat includes an abutting face having a maximum radial extent the same as the maximum radial extent of the single magnet and of the opposite end faces. One of the abutting faces has a second engaging member. The first engaging member is located at the maximum radial extent at the outer edge of the at least one of the two opposite end faces, or located at the inner edge of the at least one of the two opposite end faces.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional application of U.S. patent application Ser. No.12/951,123 filed on Nov. 22, 2010.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rotor structure for a motor and, moreparticularly, to a rotor structure that includes fixing seats securelycoupling a shaft and a magnet together.

2. Description of the Related Art

As shown in FIG. 1, a conventional rotor structure for a brushless motorincludes a shaft 10 and a magnet 20. The magnet 20 is in a shape of acylinder with an axial hole 21 extending through the magnet 20 along acenterline of the cylinder for the shaft 10 to pass through said axialhole 21. Conventionally, there are two ways to provide a linkage betweenthe shaft 10 and the magnet 20, which are linkages realized through“tight-fit design” or through “adhesive” and are discussed in detail asfollow.

The linkage between the shaft 10 and magnet 20 provided by “tight-fitdesign” is achieved by arranging the axial hole 21 of the magnet 20tightly fitting the shaft 10, in a way such that the magnet 20 iscoupled with the shaft 10 and able to synchronously revolve therewith.However, owing to the fragility of the magnet 20, coupling the shaft 10and the magnet 20 by “tight-fit design” leads the magnet 20 to ruptureeasily. Moreover, if the magnet 20 does not fit the shaft 10 tightlyenough, the shaft 10 may be disengaged from the magnet 20 due totemperature-induced expansion and contraction. Also, disengagementbetween the shaft 10 and the magnet 20 will further cause the magnet 20to be unable to synchronously revolve with the shaft 10.

Linking the shaft 10 and the magnet 20 through “adhesive” is achieved byapplying adhesive between the shaft 10 and the axial hole 21 of themagnet 20, such that the magnet 20 is coupled with the shaft 10 and ableto synchronously revolve therewith. However, the lifetime of the appliedadhesive is limited, which will not be able to provide stickiness whenthe lifetime thereof is ended. Besides, since the rotor structure isordinarily operated under high temperature and high rotational speed,the lifetime of said adhesive is easily shortened.

Accordingly, there is a need for redesigning the conventional rotorstructure.

SUMMARY OF THE INVENTION

The primary objective of this invention is to provide a rotor structurefor a motor having two fixing seats jointly positioning a magnet at apredetermined position relative to a shaft, with an axial hole of themagnet fitting with a small clearance or loosely fitting the shaft, andthe fixing seats tightly fitting said shaft. Accordingly, the magnet isprevented from rupturing or from being unable to synchronously revolvewith the shaft owing to disengagement between the shaft and the magnet.

The secondary objective of this invention is to provide the rotorstructure for a motor in which two end faces of the magnet and twoabutting faces of said fixing seats are formed with rough surfaces orcorresponding grooves and protrusions, to achieve a stable-engagingeffect between the magnet and the fixing seats.

In an embodiment of the invention, a rotor structure for a motorcomprises a shaft, a single magnet and two fixing seats. The singlemagnet has two opposite end faces. An axial hole extends along an axisthrough said two opposite end faces and has a maximum extent parallel tothe axis equal to a maximum extent parallel to the axis between the twoopposite end faces. At least one of the two opposite end faces has atleast one first engaging member being a groove extending parallel to theaxis into the at least one of the two opposite end faces. The singlemagnet and each of the two opposite end faces of the single magnet havea maximum radial extent perpendicular to the axis. Each fixing seat hasan abutting face. Each of the abutting faces has a maximum radial extentperpendicular to the axis the same as the maximum radial extent of thesingle magnet and of the two opposite end faces of the single magnet. Atleast one of the abutting faces faces said at least one of the twoopposite end faces and has at least one second engaging member facingand engaging with said at least one first engaging member. A positioninghole is disposed at the center of the abutting face. The two fixingseats have circular cross sections perpendicular to the positioning holeand to the axis. The shaft passes through the axial hole of the singlemagnet and the positioning holes of the two fixing seats. The two fixingseats are adjacent to and abut against the end faces of the singlemagnet by the abutting faces respectively to position the single magnetrelatively to the shaft. Both the positioning holes of the two fixingseats have a diameter smaller than that of said shaft to tightly fitsaid shaft. The at least one first engaging member is located at themaximum radial extent at the outer edge of the at least one of the twoopposite end faces, or located at the inner edge of the at least one ofthe two opposite end faces.

In a form shown, the axial hole of the single magnet has an equaldiameter with the shaft.

In the form shown, the axial hole of the single magnet has a diameterlarger than that of the shaft to loosely fit the shaft.

In the form shown, the at least one second engaging member is at leastone protrusion.

In the form shown, each of the two opposite end faces of the singlemagnet is formed with a rough surface, the abutting face is formed witha rough surface, and the rough surfaces of the two opposite end facesand the abutting face provide friction therebetween to stably link theshaft and the single magnet.

In another embodiment of the invention, a rotor structure for a motorcomprises a shaft, a single magnet and two fixing seats. The singlemagnet has two opposite end faces. An axial hole extends along an axisthrough said two opposite end faces and has a maximum extent parallel tothe axis equal to a maximum extent parallel to the axis between the twoopposite end faces. At least one of the two opposite end faces has atleast one first engaging member being a protrusion extending parallel tothe axis from the at least one of the two opposite end faces. The singlemagnet and each of the two opposite end faces of the single magnet havea maximum radial extent perpendicular to the axis. Each fixing seat hasan abutting face. Each of the abutting faces has a maximum radial extentperpendicular to the axis the same as the maximum radial extent of thesingle magnet and of the two opposite end faces of the single magnet. Atleast one of the abutting faces faces said at least one of the twoopposite end faces and has at least one second engaging member facingand engaging with said at least one first engaging member. A positioninghole is disposed at the center of the abutting face. The two fixingseats have circular cross sections perpendicular to the positioning holeand to the axis. The shaft passes through the axial hole of the singlemagnet and the positioning holes of the two fixing seats. The two fixingseats are adjacent to and abut against the end faces of the singlemagnet by the abutting faces respectively to position the single magnetrelatively to the shaft. Both the positioning holes of the two fixingseats have a diameter smaller than that of said shaft to tightly fitsaid shaft. The protrusion is at an inner edge or an outer edge of theat least one of the two opposite end faces.

In a form shown, the at least one second engaging member is at least onegroove.

In the form shown, the axial hole of the single magnet has an equaldiameter with the shaft.

In the form shown, the axial hole of the single magnet has a diameterlarger than that of the shaft to loosely fit the shaft.

In the form shown, each of the two opposite end faces of the singlemagnet is formed with a rough surface, the abutting face is formed witha rough surface, and the rough surfaces of the two opposite end facesand the abutting face provide friction therebetween to stably link theshaft and the single magnet.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinafter, and the accompanying drawingsthat are given by way of illustration only and are not limitations ofthe present invention, wherein:

FIG. 1 is a cross-sectional side view illustrating a conventional rotorstructure for a motor;

FIG. 2 is an exploded perspective view illustrating a rotor structurefor a motor in accordance with a first embodiment of the presentinvention;

FIG. 3 is a cross-sectional side view illustrating the rotor structurefor a motor in accordance with the first embodiment of the presentinvention;

FIG. 4 is an exploded perspective view illustrating a rotor structurefor a motor in accordance with a configuration of a second embodiment ofthe present invention;

FIG. 5 is a cross-sectional side view illustrating the rotor structurefor a motor in accordance with the configuration of the secondembodiment of the present invention;

FIG. 6 is an exploded perspective view illustrating a rotor structurefor a motor in accordance with another configuration of the secondembodiment of the present invention;

FIG. 7 is an exploded perspective view illustrating a rotor structurefor a motor in accordance with a third embodiment of the presentinvention;

FIG. 8 is a cross-sectional side view illustrating the rotor structurefor a motor in accordance with the third embodiment of the presentinvention;

FIG. 9 is an exploded perspective view illustrating a rotor structurefor a motor in accordance with a fourth embodiment of the presentinvention; and

FIG. 10 is a cross-sectional side view illustrating the rotor structurefor a motor in accordance with the fourth embodiment of the presentinvention.

In the various figures of the drawings, the same numerals designate thesame or similar parts. Furthermore, when the terms “first”, “second” andsimilar terms are used hereinafter, it should be understood that theseterms refer only to the structure shown in the drawings as it wouldappear to a person viewing the drawings and are utilized only tofacilitate describing the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIGS. 2 and 3, a rotor structure for a motor inaccordance with a first embodiment is illustrated. The rotor structureincludes a shaft 10, a magnet 20 and two fixing seats 30. The shaft 10is in a shape of a cylindrical stick. The magnet 20 is in a shape ofcylinder and has an axial hole 21 and two opposite end faces 22, withthe axial hole 21 extending between centers of said two end faces 22 andwith each of the end faces 22 being formed with a rough surface. Eachfixing seat 30 has an abutting face 32 also formed with a rough surfaceand a positioning hole 31 disposed at the center of the abutting face32.

In assembly, the shaft 10 passes through the axial hole 21 of the magnet20 and the positioning holes 31 of the fixing seats 30, with the twofixing seats 30 being adjacent to, and abutting against, the end faces22 of the magnet 20 by the abutting faces 32, respectively. Furthermore,the axial hole 21 of the magnet 20 fits with a small clearance orloosely fits the shaft 10, and both positioning holes 31 of the fixingseats 30 tightly fit said shaft 10. Specifically, the axial hole 21 ofthe magnet 20 has a diameter substantially equal to, or slightly largerthan, a diameter of the shaft 10, and both positioning holes 31 of thefixing seats 30 have a diameter smaller than the diameter of the shaft10. For example, the shaft 10 may have a diameter of 1 cm, the axialhole 21 of the magnet 20 may have a diameter of 1 to 1.03 cm, and theboth positioning holes 31 may have a diameter of 0.95 cm. The two fixingseats 30 can thereby jointly position the magnet 20 at a predeterminedposition relative to the shaft 10. Besides, great friction between theabutting faces 32 of the fixing seats 30 and the end faces 22 of themagnet 20 is provided through the rough surfaces thereof. As a result, astable linkage between the shaft 10 and the magnet 20 is achieved, andthe magnet 20 is therefore able to synchronously revolve with the shaft10.

Referring now to FIGS. 4 and 5, a rotor structure for a motor inaccordance with a configuration of a second embodiment is illustrated.The rotor structure also includes the shaft 10, a magnet 40 and twofixing seats 50. The magnet 40 has an axial hole 41 and two opposite endfaces 42, with the axial hole 41 extending between said two end faces42. Each fixing seat 50 has an abutting face 52 and a positioning hole51 disposed at the center of the abutting face 52. In assembly, theshaft 10 passes through the axial hole 41 of the magnet 40 and thepositioning holes 51 of the fixing seats 50, with the two fixing seats50 being adjacent to, and abutting against, the end faces 42 of themagnet 40 by the abutting faces 52, respectively, for jointlypositioning the magnet 40 at a predetermined position relative to theshaft 10. Furthermore, the axial hole 41 of the magnet 40 fits with asmall clearance or loosely fits the shaft 10, and both positioning holes51 of the fixing seats 50 tightly fit said shaft 10. Similarly to theabove first embodiment, the axial hole 41 of the magnet 40 has adiameter substantially equal to, or slightly larger than, a diameter ofthe shaft 10, and both positioning holes 51 of the fixing seats 50 havea diameter smaller than the diameter of the shaft 10. What is differentfrom the rotor structure of the first embodiment is that each of the endfaces 42 has at least one first engaging member 43, while each of theabutting faces 52 has at least one second engaging member 53 facing andengaging with said at least one first engaging member 43. The at leastone first engaging member 43 is preferably selected from at least onegroove or protrusion, with the at least one second engaging member 53being correspondingly selected from at least one protrusion or groove.Besides, the quantities of the at least one first engaging member 43 andthe at least one second engaging member 53 for the end faces 42 and theabutting faces 52 abutting against each other correspond to each other.

FIGS. 4 and 5 show said configuration of the second embodiment, and thequantity of the at least one first engaging member 43 is two for eachend face 42 of the magnet 40, with said two first engaging members 43being disposed at an inner edge of each end face 42 and adjacent to theaxial hole 41. The quantity of the at least one second engaging member53 is also two and said second engaging members 53 are correspondinglydisposed on the abutting face 52 of each fixing seat 50. Moreover, forsaid configuration, the at least one first engaging member 43 may beimplemented as at least one groove and the at least one second engagingmember 53 may be implemented as at least one protrusion.

Referring now to FIG. 6, a rotor structure for a motor in accordancewith another configuration of the second embodiment is illustrated.Based on the rotor structure of the configuration, structures of theshaft 10, a magnet 40′ having an axial hole 41′ and two end faces 42′with at least one first engaging member 43′, and two fixing seats 50′each having a positioning hole 51′ and an abutting face 52′ with atleast one second engaging member 53′, are similar to that of the secondembodiment. The quantities of the at least one first and second engagingmembers 43′, 53′ for each end face 42′ and abutting face 52′ are two asshown. FIG. 6 shows said another configuration of the second embodiment,although the two first engaging members 43′ are also disposed at aninner edge of each end face 42′ adjacent to the axial hole 41′ with thetwo second engaging members 53′ facing and engaging therewith, twoprotrusions are selected as the two first engaging members 43′, whiletwo grooves are selected as the two second engaging members 53′.

Referring now to FIGS. 7 and 8, a rotor structure for a motor inaccordance with a third embodiment is illustrated. Based on the rotorstructure of the third embodiment, configurations of the shaft 10, amagnet 60 having an axial hole 61 and two end faces 62 with at least onefirst engaging member 63, and two fixing seats 70 each having apositioning hole 71 and an abutting face 72 with at least one secondengaging member 73, are similar to that of the second embodiment.Although in FIGS. 7 and 8, the quantity of the at least one firstengaging member 63 is also two for each end face 62 of the magnet 60,said two first engaging members 63 are disposed at an outer edge of eachend face 62. The quantity of the at least one second engaging member 73is also two and the second engaging members 73 are correspondinglydisposed on the abutting face 72 of each fixing seat 70. Moreover,instead of the fixing seats 30, 50, 50′ each having a sleeve around thepositioning holes 31, 51 or 51′ on surfaces opposite to the abuttingfaces 32, 52 or 52′, the fixing seats 70 are in a shape of a simple flatplate or block.

Referring now to FIGS. 9 and 10, a rotor structure for a motor inaccordance with a fourth embodiment is illustrated. Based on the rotorstructure of the fourth embodiment, configurations of the shaft 10, amagnet 80 having an axial hole 81 and two end faces 82 with at least onefirst engaging member 83, and two fixing seats 90 each having apositioning hole 91 and an abutting face 92 with at least one secondengaging member 93, are also similar to that of the second embodiment.Although in FIGS. 9 and 10, the quantity of the at least one firstengaging member 83 is also two for each end face 82 of the magnet 80,said two first engaging members 83 are disposed on the end face 82between inner and outer edges thereof.

Instead of the end faces 22 and the abutting face 32 having the form ofrough surfaces of the first embodiment, the first engaging members 43,43′, 63, 83 and the second engaging members 53, 53′, 73, 93 of the otherembodiments can also provide a stable linkage between the shaft 10 andany of the magnets 20, 40, 40′, 60, 80, and the magnets 20, 40, 40′, 60,80 are therefore able to synchronously revolve with the shaft 10.Moreover, in order to provide a further stable-engaging effect betweenthe magnets 20, 40, 40′, 60, 80 and the fixing seats 30, 50, 50′, 70,90, the end faces 22, 42, 42′, 62, 82 and the abutting faces 32, 52,52′, 72, 92 can not only provide at least one pair of the first engagingmembers 43, 43′ 63, 83 and the second engaging members 53, 53′, 73, 93,but can also be formed with the rough surfaces.

In comparison with the conventional rotor structure, the presentinvention can obviously provide two improvements as follow. Firstly,because the axial holes 21, 41, 41′, 61, 81 of the magnets 20, 40, 40′,60, 80 fit with a small clearance or loosely fit the shafts 10 (i.e. theaxial holes 21, 41, 41′, 61, 81 have a diameter substantially equal toor slightly larger than the diameter of the shafts 10) while thepositioning holes 31, 51, 51′, 71, 91 of the fixing seats 30, 50, 50′,70, 90 tightly fit said shafts 10 (i.e. the positioning holes 31, 51,51′, 71, 91 have a diameter smaller than the diameter of the shaft 10),the fixing seats 30, 50, 50′, 70, 90 can thereby position each of themagnets 20, 40, 40′, 60, 80 at a predetermined position relative to eachshaft 10. Therefore, rupture of the magnet caused by a “tight-fitdesign” of the shaft 10 and the magnet 20 and disengagement between theshaft 10 and magnet 20 are avoided. Secondly, the end faces 22, 42, 42′,62, 82 of the magnet 20, 40, 40′, 60, 80 and the abutting faces 32, 52,52′, 72, 92 of the fixing seats 30, 50, 50′, 70, 90 can be formed withrough surfaces, which correspondingly provide at least one pair of firstengaging members 43, 43′, 63, 83 and second engaging members 53, 53′,73, 93, or have both the rough surfaces and said first and secondengaging members 43, 43′ 63, 83, 53, 53′ 73, 93, to achievestable-engaging effect between the magnets 20, 40, 40′, 60, 80 andfixing seats 30, 50, 50′, 70, 90.

Although the invention has been described in detail with reference toits presently preferred embodiments, it will be understood by one ofordinary skill in the art that various modifications can be made withoutdeparting from the spirit and the scope of the invention, as set forthin the appended claims.

What is claimed is:
 1. A rotor structure for a motor comprising: ashaft; a single magnet having two opposite end faces, wherein an axialhole extends along an axis through said two opposite end faces and has amaximum extent parallel to the axis equal to a maximum extent parallelto the axis between the two opposite end faces, wherein at least one ofthe two opposite end faces has at least one first engaging member beinga groove extending parallel to the axis into the at least one of the twoopposite end faces, wherein the single magnet and each of the twoopposite end faces of the single magnet have a maximum radial extentperpendicular to the axis; and two fixing seats each having an abuttingface, with each of the abutting faces having a maximum radial extentperpendicular to the axis the same as the maximum radial extent of thesingle magnet and of the two opposite end faces of the single magnet,with at least one of the abutting faces facing said at least one of thetwo opposite end faces and having at least one second engaging memberfacing and engaging with said at least one first engaging member, with apositioning hole disposed at the center of the abutting face, with thetwo fixing seats having circular cross sections perpendicular to thepositioning hole and to the axis, wherein the shaft passes through theaxial hole of the single magnet and the positioning holes of the twofixing seats, the two fixing seats are adjacent to and abut against theend faces of the single magnet by the abutting faces respectively toposition the single magnet relatively to the shaft, both the positioningholes of the two fixing seats have a diameter smaller than that of saidshaft to tightly fit said shaft, wherein the at least one first engagingmember is located at the maximum radial extent at the outer edge of theat least one of the two opposite end faces, or located at the inner edgeof the at least one of the two opposite end faces.
 2. The rotorstructure for the motor as defined in claim 1, wherein the axial hole ofthe single magnet has an equal diameter with the shaft.
 3. The rotorstructure for the motor as defined in claim 1, wherein the axial hole ofthe single magnet has a diameter larger than that of the shaft toloosely fit the shaft.
 4. The rotor structure for the motor as definedin claim 1, wherein the at least one second engaging member is at leastone protrusion.
 5. The rotor structure for the motor as defined in claim1, wherein each of the two opposite end faces of the single magnet isformed with a rough surface, the abutting face is formed with a roughsurface, and the rough surfaces of the two opposite end faces and theabutting face provide friction therebetween to stably link the shaft andthe single magnet.
 6. A rotor structure for a motor comprising: a shaft;a single magnet having two opposite end faces, wherein an axial holeextends along an axis through said two opposite end faces and has amaximum extent parallel to the axis equal to a maximum extent parallelto the axis between the two opposite end faces, wherein at least one ofthe two opposite end faces has at least one first engaging member beinga protrusion extending parallel to the axis from the at least one of thetwo opposite end faces, wherein the single magnet and each of the twoopposite end faces of the single magnet have a maximum radial extentperpendicular to the axis; and two fixing seats each having an abuttingface, with each of the abutting faces having a maximum radial extentperpendicular to the axis the same as the maximum radial extent of thesingle magnet and of the two opposite end faces of the single magnet,with at least one of the abutting faces facing said at least one of thetwo opposite end faces and having at least one second engaging memberfacing and engaging with said at least one first engaging member, with apositioning hole disposed at the center of the abutting face, with thetwo fixing seats having circular cross sections perpendicular to thepositioning hole and to the axis, wherein the shaft passes through theaxial hole of the single magnet and the positioning holes of the twofixing seats, the two fixing seats are adjacent to and abut against theend faces of the single magnet by the abutting faces respectively toposition the single magnet relatively to the shaft, both the positioningholes of the two fixing seats have a diameter smaller than that of saidshaft to tightly fit said shaft, wherein the protrusion is at an inneredge or an outer edge of the at least one of the two opposite end faces.7. The rotor structure for the motor as defined in claim 6, wherein theat least one second engaging member is at least one groove.
 8. The rotorstructure for the motor as defined in claim 6, wherein the axial hole ofthe single magnet has an equal diameter with the shaft.
 9. The rotorstructure for the motor as defined in claim 6, wherein the axial hole ofthe single magnet has a diameter larger than that of the shaft toloosely fit the shaft.
 10. The rotor structure for the motor as definedin claim 6, wherein each of the two opposite end faces of the singlemagnet is formed with a rough surface, the abutting face is formed witha rough surface, and the rough surfaces of the two opposite end facesand the abutting face provide friction therebetween to stably link theshaft and the single magnet.